BREAKING: MERS Virus 65% death rate, No Cure. Millions could be infected in Mecca during Ramadan

In the Saudi cluster that was investigated, certain patients infected many more people than would be expected, Perl said. One patient who was receiving dialysis treatment spread MERS to seven others, including fellow dialysis patients at the same hospital. During SARS, such patients were known as “superspreaders” and effectively seeded outbreaks in numerous countries.

Perl and colleagues also concluded that symptoms of both diseases are similar, with an initial fever and cough that may last for a few days before pneumonia develops.

But MERS appears far more lethal. Compared to SARS’ 8 percent death rate, the fatality rate for MERS in the Saudi outbreak was about 65 percent, though the experts could be missing mild cases that might skew the figures.

Doctors around the world have struggled to treat patients. “We need more information from other countries to find out what the best treatment is,” said Dr. Clemens Wendtner, who treated a MERS patient who later died in Munich. “Our patient got everything possible and it still didn’t help him.”